Cylinder Head Fundamentals

Question 1

What 2 materials are used for cylinder heads?

Answer 1

Cast iron alloys

Aluminum

Question 2

What factors influence the design of a cylinder head?

Answer 2

Engine application
Horsepower rating
max RPM
Method of induction

Question 3

Four-valve cylinder heads offer increased:

Answer 3

Volumetric efficiency

Turbulence

Question 4

Injector tube

Answer 4

Copper, stainless, ar brass sleeve pressed into the head. Usually surrounded by coolant to cool injector during operation

Question 5

There must be a seal between the injector tube and head to prevent?

Answer 5

Coolant from leaking past the tube into the combustion chamber and the crankcase,
Combustion from leaking past the tube into the cooling system

Question 6

Coolant and Lube passages

Answer 6

Coolant is routed through head near high heat areas.

Oil is routed from the main gallery in the block to lubricate and cool the valve operating mechanisms

Question 7

Valves preform two basic functions:

Answer 7

Open and close the cylinder to allow airflow during the intake and exhaust events
Seal the cylinder during the compression and power events

Question 8

Valve lock groove

Answer 8

Groove machined into the valve stem and mates with a lug on the valve locks. The valve locks and retainer keep the valve and valve spring together

Question 9

Valve stem

Answer 9

is the main shaft that supports the valve head. The stem fits inside valve guide in the cylinder head

Question 10

Valve Fillet

Answer 10

Area between the stem and the head, is a smooth radius for strength and stress relief. the radius also enhances air flow.

Question 11

Valve Face

Answer 11

Is a smooth, machined surface that mates with the valve seat in the head

Question 12

Valve margin

Answer 12

Is the material between the valve face and valve head. The margin supports the valve face and provides material for heat absorption. Valve should be replaced when margin is 1/2 gone

Question 13

Valve Head

Answer 13

lower end the is exposed the the combustion chamber. size of valve is determined by the diameter of the head

Question 14

Valve Tip

Answer 14

The part of the valve that is in contact with the valve operating mechanism

Question 15

One piece valve

Answer 15

Used when a single metal alloy can be used to provide all the qualities required for valve construction

Question 16

Two-piece valve

Answer 16

Allow the stem and head to be constructed of different materials. The stem must be made of a metal alloy that resists scuffing and scoring. The head must be resistant to extreme heat, pressure and corrosive gases

Question 17

Solid stem valve cooling

Answer 17

Approximately 75% of cooling occurs between valve face and valve seat, 25% is transferred from valve stem to valve guide.

Question 18

Sodium cooled exhaust valves

Answer 18

Used in severe duty applications where additional valve cooling is required. When valve heats up sodium in stem tuns to liquid acts like a shaker moving more heat out through the stem

Question 19

Valve seat

Answer 19

Sealing point between valve face and the cylinder head. Can either be integral or replaceable. Replaceable inserts are made from hardened alloy such as Stellite.

Question 20

Valve face to seat contact is necessary to:

Answer 20

Create an effective combustion chamber seal

Allow proper valve cooling

Question 21

Valve guides

Answer 21

Supports the valve to keep it square with the valve seat. Can be either integral part of head, or replaceable. Replaceable ones are made out of material that has better wear characteristics then cast iron.

Question 22

Single coil valve springs

Answer 22

Single coil spring usually have a flat inner damper coil to counteract valve spring vibrations at higher RPM’s.
Single coil springs can be either constant rate or progressive rate

Question 23

Dual coil spring assemblies

Answer 23

Have and inner and outer coil, used to increase the amount of valve spring tension over single valve springs.

Question 24

Spring seat

Answer 24

hardened washer installed under each spring to: help locate the valve spring and keep it centred over the guide, prevent erosion of the casting by keeping the spring from contacting the cylinder head material

Question 25

Valve retainers and locks

Answer 25

Retainer forms a top to keep the valve and spring as a unit, Inside bore of the retainer is tapered to match the outside of the locks.

Question 26

Valve seals

Answer 26

Positive seals: fits down over the stem and provide best control of stem lubrication
Non-positive: Acts like shield or deflector t divert the splash oil away from the valve guide and stem

Question 27

Rocker Arm tip contact surface

Answer 27

the point of the rocker arm that contacts the tip of the valve stem

Question 28

Rocker arm adjusting screw

Answer 28

provides a means for adjusting clearance in the pushrod operating mechanism

Question 29

Rocker arm bushing

Answer 29

a replaceable wear surface between the rocker arm and the shaft

Question 30

Rocker arm ratio

Answer 30

Ration that increases the valve opening compared to the actual amount of cam lobe lift

Question 31

Valve bridges

Answer 31

Also called valve crossheads, used on cylinder heads with four valves. the bridge spans a pair of common valves and allows one rocker arm to open both valves simultaneously

Question 32

What are 2 types of head gasket construction?

Answer 32

Steel

composition

Question 33

Head gasket design

Answer 33

Categorized as being one-piece or multi-piece. Engine design, horsepower rating, application are all factor that influence the type of gasket used

Question 34

The most common material used for diesel engine cylinder head construction is:

Answer 34

Cast iron alloy

Question 35

List two main benefits of a four-valve head over a two-valve head?

Answer 35

Increased volumetric efficiency

Increased turbulence

Question 36

What are the purpose of ports in the head?

Answer 36

Direct airflow in and out of the cylinder

Question 37

Why must there be a seal between the cylinder head and an injector tube?

Answer 37

Prevent coolant from leaking past the tube into the combustion chamber
Prevent combustion from leaking past the tube into the cooling system

Question 38

Explain why an exhaust valve is usually made of higher quality material than an intake valve?

Answer 38

It operates with higher temperatures and more corrosive gases

Question 39

the purpose of a carbon scraper on a valve is to prevent carbon buildup:

Answer 39

In the lower part of the valve guide

Question 40

2 benefits of having valve equipped with rotators?

Answer 40

Rotation provides a changing wear surface for more even valve and seat wear
Rotation creates wiping action that helps keep the valve face and seat clean of carbon